The textbook states that Pavlov "had to pick a stimulus that was more controlled than the sound of someone walking into a room" in order to investigate classical conditioning more systematically. In other words, Pavlov had to deliberately manipulate the neutral stimulus to conduct:
A) correlational studies.
B) case studies.
C) observational research.
D) experimental re
search.

D) experimental re search.                                              

Explanation:

Experimental research: In psychological research, the term experimental research is described as a research study that is strictly based on the "scientific research design". Experimental research tends to include a specific hypothesis, and distinct variables including dependent or an independent variable i.e, one variable is being measured or tested whereas the other variable is being manipulated or altered by the researcher.

In the question above, the given statement signifies the experimental research.

all you have to do is look at the pictures to find hope this is the lesson you were also hope this .

the branch of biology that deals with the normal functions of living organisms and their parts.

the way in which a living organism or bodily part functions.